docs: def string(self, *pattern, **kwargs):
          """
          Add string pattern
  
          :param pattern:
          :type pattern:
          :param kwargs:
          :type kwargs:
          :return:
          :rtype:
          """
          set_defaults(self._kwargs, kwargs)
          set_defaults(self._functional_defaults, kwargs)
          set_defaults(self._defaults, kwargs)
          pattern = self.rebulk.build_string(*pattern, **kwargs)
          part = ChainPart(self, pattern)
          self.parts.append(part)
          return part